The present invention generally relates to compressors for compressing refrigerant or like fluid therein and, more particularly, to a device for modulating the capacity of a compressor.
Various types of capacity modulation devices have heretofore been proposed for compressors, such as one which forces an intake valve to open for venting a cylinder bore and one which bypasses compressed fluid from a compression chamber back to the suction side. However, all these conventional types of capacity modulation devices cannot avoid intricacy of construction due to the provision of an unloading valve, a capacity regulating valve or like valving arrangement.
Another type of compressor capacity modulation device is known which is specifically directed to preventing the evaporator of an automotive air conditioning system from frosting up, as disclosed in U.S. Pat. No. 3,998,570. The device includes a second or modulating piston in addition to a usual double acting piston adapted to compress fluid in a compression chamber. A bellows is extendible within a space between the modulating piston and double acting piston to automatically modulate the displacement of the compressor. This type of device, however, suffers from various problems such as limited responsiveness and limited durability of the bellows.